Humanoid robots, for example, robots having human characteristics, represent a major step in applying autonomous machine technology toward assisting persons in the home or office. Potential applications encompass a myriad of daily activities, such as attending infants and responding to calls for information and assistance. Indoor humanoid robots may be expected to perform common household chores, such as making coffee, washing clothes, and cleaning a spill. Additional applications may include assisting elderly and handicapped persons. Humanoid robots will be expected to respond to a number of types of commands and queries from their users. Such queries may span a wide range of subject matter. For example, a query may regard a fact, such as “who is the president?” Another query type may regard a condition, such as “what is the weather?” Yet another query type may regard an observation, such as “is there food in the refrigerator?”
Some systems have manually built question hierarchies. Descriptions of this can be found in D. Moldovan, et al., Lasso: A Tool for Surfing the Answer Net, proceedings of TREC-8, pp 175-183, 1999. An alternate approach recognizes paraphrase variants. For example, Barzilay et al. analyzed 200 two-sentence themes from a corpus and extracted seven lexico-syntacetic paraphrasing rules. These rules covered 82% of syntacetic and lexical paraphrases, which in turn covered 70% of all variants. A description of this can be found in R. Barzilay, et al., Information Fusion in the Context of Multi-Document Summarization, Proceedings of ACL, 1999, which is incorporated by reference herein in its entirety. Qi et al. allowed multiple categories for questions with a probabilistic classifier. A description of this can be found in H. Qi, et al., Question Answering and Novelty Tracks, Proceedings of TREC 2002, The University of Michigan at Trec, 2002, which is incorporated by reference herein in its entirety.
AskMSR used N gram harvesting to use text patterns derived from questions to extract sequences of tokens that are likely to contain the answer, for example, five tokens to the right of “Bill Gates is married to.” The approach transformed questions into search engine queries by sample regular expression matching rules, noun-object (NO) parsing or part of speech (POS) tagging, e.g., is Gates married to, Gates is married to, Gates married is to, Gates married to is. Search engine queries were submitted to search engines that searched the Web. The responses were filtered by expected answer type, frequency of occurrence voting, and tiling by combining shorter candidates into longer candidates, for example, United Nations Children's Fund. A description of this can be found in AskMSR: Question Answering Using the Worldwide Web, M. Banko, et al., Proceedings of AAAI Spring Symposium on Mining Answers from Texts and Knowledge Bases, March 2002, which is incorporated by reference herein in its entirety.
Pasca and Harabigiu developed a large taxonomy of question types and expected answer types. A statistical parser was used to parse questions and relevant text for answers, and to build a knowledge base. Query expansion loops were used to add or delete query terms to retrieve an acceptable number of paragraphs to process further to extract answers. Once the question was categorized, it could be answered using an appropriate knowledge source. For example, for weather-related questions, a weather website would be appropriate. For definition questions, a dictionary definition, a general encyclopedia entry, or a domain specific article might be appropriate, depending on the user. A description of this can be found in M. A. Pasca, and S. M. Harabagiu, High Performance Question Answering, Proceedings of the 24th Annual International ACM SIGIR Conference on Research and Development in Information Retrieval, 2001.
Conventional QA systems utilize statistics regarding multiple answer occurrences (using voting, tiling, filtering etc) and also ensure that answers match the expected type. Answers to factual questions are typically named entities (nouns), such as locations, persons and organizations. According to Lehnert, classifying questions is important to avoid answers to questions such as Do you know the time? Yes; How did John pass the exam? With a pen. A description of this can be found in W. Lehnert, A Conceptual Theory of Question Answering, Proceedings of the Fifth international Joint Conference on Artificial Intelligence (IJCAI), 158-164, 1977, which is incorporated by reference herein in its entirety.
Conventional work in Question Answering (QA) has focused on factual QA. For example, the Text Retrieval Conference (TREC) has focused on factoid questions, for which many answers can be found on the Worldwide Web (Web). The TREC system uses word-based classification to determine an answer type for a given question, and uses linguistic techniques like reformation/pattern matching to extract possible answers. For example, for the question “When did Nixon visit China?” the answer type is Date. Reformation of the question accommodates variants like “Nixon visited china in ______,” etc. A description of this can be found in A. R. Diekema, et al., Finding Answers to Complex Questions, 2004, in M. T. Maybury, ed., New Directions in Question Answering, AAAI Press/MIT Press, 141-152, which is incorporated by reference herein in its entirety.
Conventional approaches to question classification rely on labeled examples, that is, example questions with paired answers. Unfortunately, labeled examples are relatively scarce and expensive, since manual labeling of example questions is tedious. Furthermore, conventional approaches can involve manual coding of question classification rules, which may break down in exceptional cases. In addition, conventional approaches may accommodate only factual questions. However, relatively few questions asked of an autonomous machine such as a humanoid robot will be factual in nature. Such questions will instead span responses to situations (for example, what to do when baby is crying), inquiries regarding observations and current events, commands and implicit questions (for example, statements offered to elicit a response). Thus, autonomous machines will need real-time access to the appropriate knowledge and information.
From the above, there is a need for a method and apparatus to provide an autonomous machine such as a humanoid robot with access to a variety of sources of knowledge and information, and to enable the autonomous machine to effectively categorize questions to determine which source is most likely to provide the desired answer. Furthermore, this should be accomplished without requiring a substantial number of manually labeled examples and manual coding of question classification rules.